Spontaneous, horizontally transmitted lymphomas of Syrian golden hamsters have recurred in high numbers in three epizootics in a hamster containment facility. This proposal describes isolation studies which would be conducted in an effort to identify the responsible agent. Preliminary results suggest that the agent is a sub-virus entity which transmits disease as infectious DNA. These preliminary findings would be confirmed in studies of the mechanism of transmission of the agent. Host immune factors important in resistance to primary tumor development following infection would be determined. Funds are badly needed to maintain the unique colony of hamsters which exhibit this highly tranmissible, spontaneous lymphoma. Specific attempts would be made to isolate agent from primary and subcultured tumors of inbred hamsters as well as from urine, feces, blood, uninvolved organs, peritoneal and respiratory fluids. Oncogenic extracts have recently been prepared from secondary tumors. These would be examined for virus particles and infectivity as well as for DNA capable of transmitting lymphoma. Primary lymphomas would be placed into tissue culture and attempts to isolate virus by cocultivation on a variety of target cells would be made. Identification of the agent by specific antibody neutralization studies would be undertaken. Animals with lymphoma and tumor tissue would be supplied to selected investigators in collaborative studies aimed at identifying causative agent by radioummunoassay of viral associated antigens. The ultimate objective is to identify the agent and to describe the mechanism of spread of this most unusual disease.